Question

The mean of 15 numbers is 12. An extra number is included and the mean increases to 13. What the extra number?

Answer 1

Answer: 28

Step-by-step explanation:

The mean of 15 numbers = 12

Then , the sum of the numbers = 12x15 = 180

Let the extra number included be $x$ , then

The new sum = $x + 180$

And the new total number will increase from 15 to 16

new mean = 13 , so we have :

$\frac{x+180}{16} = 13$

$x+ 180 = 16(13)$

$x + 180 = 208$

$x = 208 - 180$

$x = 28$

therefore , the extra number is 28